[cupertino_icons] Remove empty Dart file (#11308)

It used to be impossible to publish a package without a lib/ directory, which is why there is a placeholder file. That hasn't been true for quite a while, however, so we don't need to keep shipping an empty file.

This will also fix the questionable pana score deduction for not having any documentation (without us having to add a library directive just to document that no code is needed).

Part of flutter/flutter#183844

## Pre-Review Checklist

[^1]: Regular contributors who have demonstrated familiarity with the repository guidelines only need to comment if the PR is not auto-exempted by repo tooling.

Author: stuartmorgan-g

third_party/packages/cupertino_icons/CHANGELOG.md

@@ -1,5 +1,6 @@
-## NEXT
+## 1.0.9
 
+* Removes empty Dart file.
 * Updates minimum supported SDK version to Flutter 3.35/Dart 3.9.
 
 ## 1.0.8

third_party/packages/cupertino_icons/lib/cupertino_icons.dart

@@ -3,7 +3,7 @@ name: cupertino_icons
 description: Default icons asset for Cupertino widgets based on Apple styled icons
 repository: https://github.com/flutter/packages/tree/main/third_party/packages/cupertino_icons
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+cupertino_icons%22
-version: 1.0.8
+version: 1.0.9
 
 environment:
   sdk: ^3.9.0